1. Field of the Invention
The present invention relates to novel biological insecticides. More specifically, this invention relates to novel strains of Bacillus thuringiensis, "B. thuringiensis," the method of their production and the method of use thereof as biological insecticides to control insect species of the order of Lepidoptera, in particularly the Trichoplusia ni, "the cabbage looper" and the Artogeia rapae, "the imported cabbageworm."
2. Description of the Prior Art
The spore forming microorganism B. thuringiensis was isolated over 80 years ago and has since become commercially prominent for biological control. The sporulating cells of B. thuringiensis each produce a spore (endospore) and a diamond-shaped proteinaceous crystal (paraspore or inclusion body). The entomocidal properties have been attributed solely to the .delta.-endotoxin which is a major component of the parasporal crystal. When the crystal solubilizes in the insect gut, it gives rise to a protoxin which is activated by proteolytic digestion.
Although quite specific for lepidopteran insects and certain flies and mosquitoes, B. thuringiensis is harmless to non-susceptible orders of insects, animal and man. Currently in the United States, B. thuringiensis var. kurstaki comprises the B. thuringiensis insecticidal products most widely-used for control of these pests. However, these products lack effective control at economical levels of application.
On the other hand, synthetic pyrethroids are the chemical insecticidal agents most widely-used for control of lepidopteran pests. Pyrethroids are highly effective and offer increased control over the currently used B. thuringiensis insecticidal products. A disadvantageous feature associated with the use of pyrethroids, however, lies in the fact that they are toxic to non-targeted invertebrates, thereby, presenting an environmental hazard to aquatic life. Consequently, there exists a need for effective lepidopteran-active insecticides which are environmentally safe and cost effective, and which duplicate the efficacy of synthetic pyrethroids.